This invention relates generally to imaging arrays, and more particularly, to pixel formations for imaging arrays.
Imaging arrays for detecting x-rays typically include a photosensor array coupled to a scintillating medium. Radiation absorbed in the scintillator generates optical photons which in turn pass into a photosensor, such as a photodiode. The photon is absorbed in the photosensor and an electrical signal corresponding to an incident photon flux is generated. Hydrogenated amorphous silicon (a-Si:H) is commonly used in the fabrication of photosensors due to advantageous photoelectric characteristics of a-Si:H and a relative ease of fabricating such devices. In particular, a plurality of photosensitive elements, such as photodiodes, can be formed in connection with any necessary control or switching elements, such as a thin film transistor (TFT), in a relatively large array. Radiation detectors and display arrays are typically fabricated on a large substrate on which many components, including TFTs, address lines, capacitors, and devices such as photosensors, are formed through the deposition and patterning of layers of conductive, semiconductive, and insulative materials.
At least one known fabrication process for such a TFT array typically includes fabricating a bottom gate TFT and a plurality of data and scan address lines. In some known bottom gate TFTs, the bottom gate metal shields a channel region, i.e. acts as a light blocking element, blocking light from a back light. The light blocking layer is desirable since photons can create an undesirable leakage in the TFT. For example, in a digital x-ray panel, the light is created from a scintillator that is deposited on the top of the devices which directly exposes the TFT regions to photons. Therefore, an additional light blocking layer, requiring an additional photolithography level, is therefore necessary to shield the TFT channel region from undesirable light.